There is a continuing need for development of methods of accurately dropping inflatable devices from an aircraft, for example, life rafts to survivors in a body of water. The most advanced method, presently in use, is dropping an inflatable device in a deployment container using a parachute and a timer as disclosed, for example, in U.S. Pat. No. 4,639,229. Use of the parachute substantially ensures correct orientation of the container on impact with the body of water and a predetermined range of speed at impact through aerodynamically braking the descent of the container. After impact the container is partially or completely submerged in the water, bobbing in the water and then floating on the surface until the device is inflated. Using a timer, the inflation is initiated after a preset time interval elapses, predetermined at time of manufacturing the inflatable device based on an expected altitude of an aircraft flying above the water surface such that the inflation starts shortly after impact of the container on the body of water. However, the exact timing for initiating the inflation is a major problem of the method of air deployment using a timer. If the inflation is initiated too early, the device is inflated while still in the air resulting in the inflated device being blown away from a target zone in the presence of wind—even at a relatively small wind speed. On the other hand, if the inflation is initiated too late the container is floating on the surface for a considerable amount of time reducing the likelihood of the device being inflated in its proper orientation. In most rescue operations survivors have to be rescued from rough seas. Under such conditions it is likely for a container to be toppled by the rough sea while floating on the surface resulting in the device being inflated upside down rendering it problematic for rescuing survivors. One solution to this problem is the use of a reversible life raft as taught in U.S. Pat. No. 6,375,529. However, use of a reversible life raft requires physical action from survivors—people in distress—in order to set up a canopy for protecting them from the elements. In particular, for rescue operations in cold climates it is essential to provide life rafts with a canopy in order to protect survivors from hypothermia.
Auto-inflation of life vests and other personal floatation devices using water activated inflators is known in the art. Water activated inflators using a water soluble element for holding a membrane piercing mechanism in a cocked position are disclosed, for example, in U.S. Pat. Nos. 6,589,087; 5,852,986; 5,694,986; 5,370,567; and 5,333,656.
In order to quickly inflate a large floatation device such as a life raft, a large gas flow is needed. Therefore, the inflator has to quickly open a sealing mechanism of a gas cylinder containing a large volume of gas under high pressure. In order to quickly and reliably create a large opening, it is preferred to provide a sufficient stroke to a valve—defining the opening—of the sealing mechanism, rather than piercing a sealing membrane. However, for providing a sufficient stroke a relatively strong force acting along a relatively long distance is applied. Timed actuators, explosive actuators, and electronic actuators are typically used to provide the force and distance required in inflating a large inflatable device. As is evident to those of skill in the art, such devices cause serious storage and maintenance problems as well as safety problems during transport in an aircraft and, therefore, are not considered useful for air rescue missions. Conversely, none of the passive water activated devices provide for the force and distance of operation required for quickly and reliably inflating a life raft.
It would be advantageous to provide a passive water activated device for supporting inflation of a life raft.